fix: rebuild nodes by default on reconcile

Do not skip node rebuilds unless SKIP_REBUILD=1 is explicitly set. This prevents stale remote helper scripts from being reused across retries after bootstrap logic changes.

nixos/kubeadm/bootstrap/controller.py

@@ -123,6 +123,7 @@ class Controller:
         self.rebuild_retries = int(self.env.get("REBUILD_RETRIES", "2"))
         self.worker_parallelism = int(self.env.get("WORKER_PARALLELISM", "3"))
         self.fast_mode = self.env.get("FAST_MODE", "1")
+        self.skip_rebuild = self.env.get("SKIP_REBUILD", "0") == "1"
 
     def log(self, msg):
         print(f"==> {msg}")
@@ -255,7 +256,7 @@ class Controller:
         self.mark_done("preflight_done")
 
     def stage_rebuild(self):
-        if self.stage_done("nodes_rebuilt"):
+        if self.skip_rebuild and self.stage_done("nodes_rebuilt"):
             self.log("Node rebuild already complete")
             return